The present invention relates to a method for producing a coated composite component. More particularly, the present invention relates to a method to fabricate composite components from a thermoplastic plastic support by coating, for example, with polyurethane, to produce various desired surface structures or haptics.
It is known to form a polyurethane skin in a first method step. A skin of this type can be produced, for example, using a so-called slush process or a spray process. In a slush process, a plastic powder or a plastic granulate is melted in an electroform whereby the material is deposited by forming a corresponding layer on the vessel wall. When spraying a polyurethane material, this material is applied to the corresponding surface by a spray process. In both processes, the fully cured skin is removed from the mold and back-injection-molded with a thermoplastic plastic material in a separate process step. This process is also referred to as “SkinForm Process” (SkinForm=trademark of Krauss-Maffei Kunststofftechnik GmbH). Such method for overcoating a skin is described in DE 699 05 745 T2 or EP 0 995 568 A1. The first document describes different alternatives for a method for producing a multilayered synthetic molded part, wherein initially a skin is produced—for example by a spray process—which is then back-injection-molded in a second production step in various ways.
In process flows currently known, a closed mold with a closed cavity is typically used for fin-free overflooding of a thermoplastic support component with a polyurethane material in a fully automated cycle. Venting of the cavity which is necessary for filling in the polyurethane material remains a problem. Almost all polyurethane systems must be thoroughly vented, which is particularly important for foamed systems. After each venting operation, the component must be reworked—albeit sometimes only slightly—in order to remove the sprues or projections formed in the vent cavities. The necessary venting operation frequently also limits the design choices.
In addition, devices and methods for producing décor materials which are back-molded with a thermoplastic material are known since quite some time. One example of this technology is disclosed in EP 0 543 085. According to the teachings therein, a décor layer is clamped between two molds. A not yet cured thermoplastic material is applied on one of the molds, which is molded, when the molds close, over the décor layer in an molding step commensurate with the cavity design of the mold. The formed part with the décor can be removed after cooling, whereby the thermoplastic material represents the support. This process is therefore very similar to the aforementioned SkinForm process.
It would therefore be desirable and advantageous to provide an improved method for producing composite components, which obviates prior art shortcomings and is able to specifically to eliminate venting of the mold.